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monoflo help

smatt302smatt302 Member Posts: 11
Im curently having trouble with my monoflow system and im not sure what it is since i made a few changes at one time i replaced the old american standard boiler with a crown boiler i changed the bg series 100 pump part number 106189 with a bg nrf-22 103251 and i took out the old t stat and put in a new one i also added another zone in the basement witch has a taco 007 pump on it and is piped in series I also added flow control valves The new zone i put in works fine the monoflo is where i am having trouble its is 1 1/4 pipe for the main with 1/2 branches feeding cast on radiators and cast iron base board The Problem is the house heats up to the setpoint of 70 not sure the amount of time it takes to get there but seems a little long then when the temp drops and the boiler calls for heat by the time it gets the house back up to temp its dropped to 66 67 degress and its cold any advice please let me know Also sorry for the run on sentences my period button on my laptop is broken thanks you


  • Paul48Paul48 Member Posts: 4,256

    You interupted the 1.25" main at the 007, pump the zone back into the main?
  • smatt302smatt302 Member Posts: 11

    i have a 1 1/4 manifold on each side of the boiler the taco pumps out of the manifold in 3/4 inch pipe and returns to the other manifold and the monoflo leaves and returns through the 1 1/4 pipe the pumps are on the return side and the flow control valves are on the feed side the pumps push throught the boiler then to the air scoop then to each flow control valve
  • Paul48Paul48 Member Posts: 4,256
    I'll Bet

    that either one of those zones running by itself work fine?
  • smatt302smatt302 Member Posts: 11

    that zone works fine but its not a monoflo system the monflo system takes to long to recover it drops 4 deg before it gets hot in the house again the only thing i can think of is the new pump spins at 2940rpm and the old one was 1725 not sure if that will effect that style system
  • Paul48Paul48 Member Posts: 4,256

    You are controlling them as seperate zones, with their own t-stats?
  • smatt302smatt302 Member Posts: 11

    the taco pump has its own and the bg has its own and is going through the argo relay
  • billbill Member Posts: 429
    edited January 2014
    Pump location

    Putting the pumps where the flow control valves are now would allow both loops to see an increase in system loop pressure. You know, pumping away.
  • smatt302smatt302 Member Posts: 11
    I thought

    The pumps were supposed to be on the return side and push through the boiler
  • billbill Member Posts: 429
    First a crash course

    Scroll up to the top of the site and click on systems. Click on hot water, then on circulars and then point of no pressure change. Also, wither the pump. For now just take the authors word for it. Explaining that in plain English is a trip.

    If it were me I would remove those flow control valves (Ball valves for that matter) and throw on the pumps. Purge thoroughly

    BTW while there I would stick the fill valve between the expansion tank and air separator
  • IronmanIronman Member Posts: 3,542

    Are you 100% certain that mono flow zone is completely purged of air? CI baseboards have to be bled at each rad and a mono flow is by far the hardest system purge.

    The rpm of the pump has nothing to do with it.

    What is the static fill pressure when the system is cool? The higher it is, the easier to bleed, but I'd keep it at or below 18psi cold.

    The location of the circ is critical. For years manufacturers put them on the return because their shipping department decided it made things easier. This gave people the idea that was the correct place for it; the engineering department knew better.

    The circ should pump away from the Point Of No Pressure Change (PONPC). This the place where the expansion tank connects to the system. If it does, then the pressure differential that the circ creates is added to the static fill pressure.

    If the circ is pumping towards the PONPC, as your is, then the pressure differential that the circ creates is deducted from the static fill pressure. This means that you could actually be running in a vacuum at the top of your loop. That would allow air to remain trapped there which could bind water flow.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • smatt302smatt302 Member Posts: 11
    i have

    bleed them through each radiator by closing the valve on all the radiators then bleeding them one at a time following the loop around so basicly what im getting is if i move the pump my ststem should heat up quicker my other question is if the pump turns on for the one zone what prevents it from pushing water through the other zone is it just the pump isnt turning
  • Paul48Paul48 Member Posts: 4,256

    What is the hi-limit set to on the boiler?
  • smatt302smatt302 Member Posts: 11


    Is it possible that when one zones pump goes on it is pumping the heat through both
  • Paul48Paul48 Member Posts: 4,256
    Not Likely

    With the flow controls present.Unless you have one, or both in their raised position.
  • Paul48Paul48 Member Posts: 4,256
    edited January 2014

    Only the monoflow zone running, are all the baseboards and radiators, on that zone getting hot?
  • smatt302smatt302 Member Posts: 11

    All radiators and baseboard get really hot but once the house gets to set point and then cools down the heating system takes to long before it recovers and the house temp has dropped from 70 to 67
  • Paul48Paul48 Member Posts: 4,256
    Heat Loss

    You need to do a heat loss, then check the radiation against that,room by room.Stand-up cast iron radiators have very different heating characteristics than cast iron baseboard.This winter has been colder than it has been in lifetimes. There has been many opportunities for folks to see their system under-perform.The changes you made to the system may have had no bad effect.Its just colder than a witches t-t out there.
  • smatt302smatt302 Member Posts: 11

    You think it would make sense to pull out the monoflo system and run 3/4 pipe in and out of each radiator in series
  • smatt302smatt302 Member Posts: 11

    It be possible that my boiler is undersized and how can I determine this
  • Paul48Paul48 Member Posts: 4,256
    Heat Loss

    That's how you size a boiler, to start with.
  • smatt302smatt302 Member Posts: 11

    Did have someone do all the calculations but I just feel 52000 buy is low
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